1. Field of the Invention
This invention relates to gas lift apparatus for wells and more particularly to side pocket mandrels for use in gas lift wells.
2. Description of the Prior Art
Side pocket mandrels have long been used in wells for many years with good results, but as gas lift techniques are practiced at greater and greater depths in wells, demands for stronger side pocket mandrels increase.
Side pocket mandrels are necessarily somewhat bulbous in structure and have appreciable lateral area subjected to internal and external pressures which tend to rupture or collapse them, and they are not well suited to resist such forces acting upon them.
Further, many mandrels are used in wells equipped with dual tubing strings and, therefore, are flattened to a generally oval cross section to permit the passage of one mandrel past another in casing of reasonable size so that either such tubing string can be pulled from the well without disturbing the other tubing string. Flattened or oval cross-section mandrels are not as strong as round mandrels and will burst or collapse at lesser pressures.
Many mandrels have been equipped with means called deflectors or discriminators immediately above their receptacle bores to ward off most well tools lowered through the tubing to avoid their lodging in the mandrel, yet permit flow control devices to be installed in or removed from their receptacle bores through use of kickover tools using conventional wireline or pumpdown (TFL) equipment and techniques. These accessories have been secured to the mandrel by welding. They have been expensive, and the welding has been a source of failure, especially where longitudinal structural welds or plug welds have been used. In some cases, wireline or tools have been damaged by or caused to lodge against such accessories and sometimes causing workover operations to be performed on a well.
In general, side pocket mandrels for use in wells where they may be subjected to severe pressure conditions where, for instance, the pressure external of the mandrel exceeds that internal thereof by as much as 10,000 to 15,000 psi or even more have been desired, but conventional structures did not lend themselves well to such rigid requirements since their size would be unduly large and require larger well casing.
U.S. patent application Ser. No. 148,928, filed May 12, 1980 by Robert S. Higgins and David T. Merritt for SIDE POCKET MANDREL AND METHOD OF CONSTRUCTION, .[.now allowed and.]. incorporated herein for all purposes, discloses a new side pocket mandrel structure and method of constructing the same whereby much stronger mandrels can be made. In this mandrel, all longitudinal structural welds and plug welds have been eliminated, thus eliminating a source of mandrel failure, however, the deflectors are welded to the inner wall of the mandrel (but not by structural welds). The present invention is an improvement over the just-mentioned invention of Higgins and Merritt, Ser. No. 148,928. In the present invention, deflectors have been eliminated altogether and in such manner that the side pocket mandrel is made much stronger both in burst strength and in collapse strength, and its cost of construction has not particularly been increased.
A search of the prior art was made, and the following U.S. patents were found:
______________________________________ 2,664,162 3,741,299 4,106,564 2,679,903 3,802,503 4,197,909 2,679,904 3,994,339 4,201,265 2,824,525 4,106,563 4,271,902 3,268,006 ______________________________________
Also found, in addition to the U.S. application Ser. No. 148,928 of Higgins and Merritt, supra, was an advertisement in WORLD OIL magazine, Aug. 15, 1981 Edition, showing a side pocket mandrel which is of interest. The advertiser is McMURRY/HUGHES, Huntsville, Texas.
U.S. Pat. No. 4,271,902 which issued June 9, 1981 to Howard H. Moore, Jr. for SELF-DISCRIMINATING SIDE POCKET MANDREL AND METHOD OF MANUFACTURING SAME discloses a side pocket mandrel having a main passage through it and a receptacle bore extending alongside the main passage. A longitudinal groove is provided in the inner wall of the mandrel and extends upwardly from the receptacle bore to a point near the upper end of the mandrel to provide space above the receptacle for operation of a kickover tool for inserting a flow control device in the receptacle bore. This structure is fabricated by welding two slotted tubes together with their slots in communication with each other to form the main bore and groove configuration. This requires long longitudinal welds, one along either side of the mandrel, and longitudinal welds, as well as plug welds, in mandrels has been a source of failure as explained in the allowed application of Higgins and Merritt, Ser. No. 148,928, supra, now U.S. Pat. No. 4,333,527 of which this present invention is an improvement.
The advertisement of McMurray/Hughes in WORLD OIL Magazine, Aug. 15, 1981 Edition, shows a cross-sectional view of a side pocket mandrel which, at first, appears to be pertinent to this case, but the description which accompanies the view makes it appear that the mandrel is constructed approximately as taught in U.S. Pat. No. 4,271,902, mentioned above, in that it is formed by joining two separate tubes together. This would require two longitudinal welds, one on either side of the mandrel, and such welds are a known source of mandrel failure.
U.S. Pat. No. 2,824,525 to McGowen shows a cross-sectional view which provides a main passage and a groove in the wall thereof, but the groove is not for operating a kickover tool, and it does not extend above the receptacle. Also, longitudinal welds are seen at W2 in FIGS. 4 and 5 and at W1 in FIG. 6.
U.S. Pat. No. 3,268,006 to Hayes shows a guide extending a short distance above the receptacle bore of a side pocket mandrel. The groove provided by this guide is of a different width for each mandrel in the tubing string with the narrowest groove in the uppermost mandrel and the widest groove in the lowermost mandrel. Rings of different sizes may be used on the kickover tool to thus provide a selectivity whereby a flow control device may be installed in a selected one of a plurality of such side pocket mandrels in a single string of well tubing.
U.S. Pat. Nos. 2,664,162 and 2,679,904 to Howard et al. show mandrels with cross sections which may be of interest in that they have a main passage and groove configuration, but this groove-like configuration runs out a short distance above the receptacle. These mandrels are not for use with kickover tools which are kicked over mechanically but were to be used with installing tools which were lowered in the well on an electric line and forced laterally to one side by magnetic forces.
U.S. Pat. Nos. 3,741,299, 3,802,503, 4,106,564, 4,106,563, 4,197,908 and 4,201,265 show side pocket mandrels having guide means or deflectors above their receptacles which provide a short longitudinal groove, but these are welded into the body and are not formed integral therewith.
U.S. Pat. No. 3,994,339 discloses side pocket mandrels having bodies of oval section. Their walls appear to be of uniform thickness, and no groove extends above their receptacle. Any increase in strength is had because of their oval, or elliptical, or egg-shaped section.
None of the prior art found in the search or with which the applicants are familiar shows an upper body section welded by a circumferential weld to the main body section of a side pocket mandrel, the upper body section providing a main passage therethrough with a longitudinal groove in the inner wall of the main passage and extending from the receptacle bore upwardly virtually to connection means at the upper end thereof to provide space above the receptacle bore for operation of a kickover tool.
The present invention overcomes the problems and shortcomings discussed hereinabove by providing side pocket mandrels in which a longitudinal groove extends upwardly from the receptacle bore to substantially the connection means on the upper end of the mandrel, this upper body portion being of uniform section, its body wall thickened on either side of the groove in a manner which strengthens the body against forces which tend to either burst or collapse it. This uniform section is provided without longitudinal or plug-type structural welds, and production of this new side pocket mandrel is economical, its structure much stronger, and it fills a longfelt need for a side pocket mandrel for use at greater depths in deeper wells where they are subjected to greater forces which would tend to destroy the mandrel by bursting or collapsing the same.